@MrT69 - quick issue, (I know you're busy with much...), not a big problem, just reporting - When I have Keweon certificate installed, repository apps won't get a connection. I'm on Sailfish OS, so mainly I get it with apps that connect to openrepos.net, (Warehouse app, Storeman app...). However, I also had the same problem on Android, with Xposed repository. Easy workaround is to use certificate mgr to uninstall certificate, connect to repos to check updates, etc, then reinstall certificate.
Is it just an issue of whitelisting, or something else?
The certificate is responsible to terminate all the HTTPS errors because of blocking HTTPS domains. You will get a 200 answewhich shows everything is fine.
Interesting thing and currently no idea why. The only thing I can offer is to connect to my private server an log everything to see what's going wrong.